RF Modulator

Quick Voltage Reference

The Astrocade uses 4 different voltages with no clear test points for taking measurements. The pictures below show a few places to take measurements and the locations of the regulators.

AC input voltage, test points at rectifier diodes.

+5, +10 points on U17 and U19

-5, +5, +12 points on RAMs U24-U31

Schematics

Full sheet schematic

UM1291-1 Modulator

Service Manual

Bally Arcade Service Manual

Overheating Chips

Heat is a notorious killer of Astrocade consoles due to air circulation problems.

An Astrocade should never be left on a carpeted surface, or in any location where heat cannot convect through and away from the console.

Inside, a large bank of chips is covered by RF shielding. Many Astrocade owners opt to improve airflow by removing this shielding. In a peculiar design choice, attached to that shielding is a "heat sink" for one of the 40-pin DIP chips. I put heat sink in quotes because it's really just a bar of metal with no cooling fins. (We have upgraded heat sinks that are more effective)

If the shielding is removed, a proper heatsink and thermal compound should be used on that chip. Even if you don't remove that shielding, a proper heatsink wouldn't hurt.

Note that the 15uF parts may be black tantalum capacitors. Later revisions of the Astrocade feature electrolytic capacitors. You might consider replacing the tantalum caps with electrolytic as tantalum caps are also prone to failure.